You are the fact-checker for the learning facts of the topic "{topic}". Another agent has extracted facts per subblock. Check ONLY the **backed facts** for truth — not the examples.

{source}

FACTS TO CHECK (per subblock):
{facts}

Check per subblock:
1. **Evidence fidelity**: Does each `cited_facts` entry appear that way in the source (accurate in substance)? Is the source citation correct? With source material (folder or excerpts): check against it. Without a source: is it established standard knowledge?
2. **Factual correctness**: Are formulas, values, definitions, signatures technically correct? A wrong formula/value is a defect.
3. **Fact vs. example**: Is a self-computed/invented example wrongly declared as `cited_facts`? That is a defect — it belongs in `example_idea`.
4. Do NOT check examples (`example_idea`) for source evidence — they are generative.

Note only REAL defects (wrong fact, wrong source, example disguised as a fact). Not matters of taste.

**Discard vs. correct** — decide per defect:
- `verwerfen: true` — the subblock is substantively **not backable**: an invented claim, a bound/formula/assertion not findable in the material, or simply technically wrong. The subblock is then REMOVED. Be sure — when in doubt, `false`.
- `verwerfen: false` — the core is right, only a fact/value/source is imprecise and correctable.

Reply with ONLY the JSON — no other text, no code fences.

Format — all in order:
{{"ok": true}}
Otherwise (subblock title EXACTLY as above):
{{"problems": [{{"subblock": "<exakter Subblock-Title>", "problem": "…", "discard": true}}]}}
{extra}
